Injection apparatuses are known as apparatuses for molding a desired product by injecting a molding material into a mold and filling the mold with the molding material. In recent injection apparatuses, for example, operating force is imparted to an injection cylinder using an electric motor as in the injection apparatus described in Patent Document 1. The injection apparatus described in this publication includes an injection cylinder device which operates an injection plunger for injecting a molding material into a mold and a conversion cylinder device which supplies hydraulic oil to the injection cylinder device. In the injection apparatus, an electric motor is used as a drive source for a conversion piston of the conversion cylinder device when supplying the hydraulic oil to the injection cylinder device. Due to this, the conversion piston of the conversion cylinder device operates with the driving force of the electric motor to supply hydraulic oil to the injection cylinder device. Due to this, the injection piston of the injection cylinder device operates toward the injecting direction of the molding material with the hydraulic oil supplied.